US11051772B2 - Filtration methods for dual-energy X-ray CT - Google Patents
Filtration methods for dual-energy X-ray CT Download PDFInfo
- Publication number
- US11051772B2 US11051772B2 US16/294,438 US201916294438A US11051772B2 US 11051772 B2 US11051772 B2 US 11051772B2 US 201916294438 A US201916294438 A US 201916294438A US 11051772 B2 US11051772 B2 US 11051772B2
- Authority
- US
- United States
- Prior art keywords
- grating
- filter
- ray
- source
- absorption
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active, expires
Links
- 238000001914 filtration Methods 0.000 title description 47
- 238000010521 absorption reaction Methods 0.000 claims abstract description 217
- 238000002591 computed tomography Methods 0.000 claims abstract description 98
- 230000005855 radiation Effects 0.000 claims abstract description 49
- 239000000463 material Substances 0.000 claims description 72
- 238000001228 spectrum Methods 0.000 claims description 40
- 238000003384 imaging method Methods 0.000 claims description 30
- 238000002083 X-ray spectrum Methods 0.000 claims description 17
- 230000000903 blocking effect Effects 0.000 claims description 8
- 238000000034 method Methods 0.000 abstract description 77
- 230000003595 spectral effect Effects 0.000 abstract description 40
- 238000000926 separation method Methods 0.000 abstract description 26
- 230000010355 oscillation Effects 0.000 abstract description 19
- 230000007423 decrease Effects 0.000 abstract description 6
- 230000001360 synchronised effect Effects 0.000 abstract description 6
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 39
- 230000004907 flux Effects 0.000 description 35
- 239000006096 absorbing agent Substances 0.000 description 25
- 238000004088 simulation Methods 0.000 description 23
- 239000007787 solid Substances 0.000 description 15
- 238000006073 displacement reaction Methods 0.000 description 14
- 238000005516 engineering process Methods 0.000 description 12
- 229910052751 metal Inorganic materials 0.000 description 12
- 239000002184 metal Substances 0.000 description 12
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 11
- 239000010931 gold Substances 0.000 description 11
- 229910052737 gold Inorganic materials 0.000 description 11
- 239000002355 dual-layer Substances 0.000 description 10
- 230000006870 function Effects 0.000 description 10
- 238000001514 detection method Methods 0.000 description 8
- 238000009826 distribution Methods 0.000 description 8
- 230000002829 reductive effect Effects 0.000 description 8
- 238000013170 computed tomography imaging Methods 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 230000008901 benefit Effects 0.000 description 6
- 230000015654 memory Effects 0.000 description 6
- 238000013459 approach Methods 0.000 description 5
- 239000000919 ceramic Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 229910052688 Gadolinium Inorganic materials 0.000 description 4
- 241000124008 Mammalia Species 0.000 description 4
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 4
- 230000008859 change Effects 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 4
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 239000010936 titanium Substances 0.000 description 4
- 229910052719 titanium Inorganic materials 0.000 description 4
- 230000001133 acceleration Effects 0.000 description 3
- 210000000038 chest Anatomy 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 230000000670 limiting effect Effects 0.000 description 3
- 230000005291 magnetic effect Effects 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 230000002123 temporal effect Effects 0.000 description 3
- 238000013519 translation Methods 0.000 description 3
- 230000014616 translation Effects 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000010247 heart contraction Effects 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 230000029058 respiratory gaseous exchange Effects 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 239000011358 absorbing material Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 239000008280 blood Substances 0.000 description 1
- 210000000988 bone and bone Anatomy 0.000 description 1
- 238000002247 constant time method Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000005294 ferromagnetic effect Effects 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000010606 normalization Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000012805 post-processing Methods 0.000 description 1
- 238000007781 pre-processing Methods 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 230000002040 relaxant effect Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000012358 sourcing Methods 0.000 description 1
- 230000036962 time dependent Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/02—Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
- A61B6/03—Computed tomography [CT]
- A61B6/032—Transmission computed tomography [CT]
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/40—Arrangements for generating radiation specially adapted for radiation diagnosis
- A61B6/4035—Arrangements for generating radiation specially adapted for radiation diagnosis the source being combined with a filter or grating
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/40—Arrangements for generating radiation specially adapted for radiation diagnosis
- A61B6/4064—Arrangements for generating radiation specially adapted for radiation diagnosis specially adapted for producing a particular type of beam
- A61B6/4085—Cone-beams
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/48—Diagnostic techniques
- A61B6/482—Diagnostic techniques involving multiple energy imaging
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
- A61B6/5258—Devices using data or image processing specially adapted for radiation diagnosis involving detection or reduction of artifacts or noise
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/40—Arrangements for generating radiation specially adapted for radiation diagnosis
- A61B6/4007—Arrangements for generating radiation specially adapted for radiation diagnosis characterised by using a plurality of source units
Definitions
- kVp-switching is an X-ray source technology in which low- and high-energy X-ray beams are alternatingly emitted during a scan.
- the dual-layer detector method is based on a detector innovation so that low- and high-energy data are collected in two sensor layers respectively. These two methods both use a single X-ray source to generate dual-energy datasets. Thus, the resultant low- and high-energy datasets share the same X-ray filter placed in front of the X-ray source.
- a dual-source system includes two imaging subsystems.
- the dual-source CT system is more expensive, and there is a temporal discrepancy between low- and high-energy data acquisitions. Breathing, heart beating, and patient motion causes artifacts in reconstructed images, compromising material decomposition and monochromatic imaging.
- Embodiments of the subject invention include systems and method for performing X-ray computed tomography (CT) that can improve spectral separation and decrease motion artifacts without increasing radiation dose to which a patient is exposed during imaging.
- CT computed tomography
- Systems and methods of embodiments of the subject invention can be used with either a kVp-switching source or a single-kVp source.
- an absorption grating and a filter grating can be disposed between the X-ray source and where a sample/patient to be imaged would be (or is) located (e.g., in front of the X-ray source).
- Relative motion of the filter and absorption gratings can by synchronized to the kVp switching frequency of the X-ray source. Different filter regions can be exposed to X-rays at various time instants, thereby producing low- and high-energy X-rays accordingly.
- a combination of absorption and filter gratings can be used and can be driven in an oscillation movement that is optimized for a single-kVp X-ray source, in certain embodiments, only a filter grating alone is required, and the filter grating can be stationary with respect to the X-ray source.
- the filter grating can be just a two-strip filter.
- a system for performing X-ray CT imaging can comprise: an X-ray source; a detector for detecting X-ray radiation from the source; a filter grating disposed between the source and the detector; and an absorption grating disposed between the filter grating and the source. At least one of the absorption grating and the filter grating can be configured to move relative to the other during operation of the source.
- the filter grating can be positioned closer to the source than it is to the detector (for example, in front of the source).
- the source can be either a kVp-switching source or a non-kVp-switching source, and the oscillation (relative movement) between the gratings can be optimized depending on what type of source is used.
- a system for performing X-ray CT imaging can comprise; a single-kVp X-ray source (non-kVp-switching X-ray source); a detector for detecting X-ray radiation from the source; and a filter grating disposed between the source and the detector.
- the filter grating can be positioned closer to the source than it is to the detector (for example, in front of the source), and the system can specifically exclude an absorption grating.
- the filter grating can be configured to be stationary during operation of the source.
- Image reconstruction for such a system can be based on a non-linear X-ray data generation model.
- the image reconstruction can include non-linear data modeling and compressed sensing.
- the present technology combines an absorption grating and a filter grating in front of an x-ray source, and moves one grating with respect to the other for a nearly instantaneous filter change.
- the relative motion is small and is synchronized with source kVp-switching and/or detector-view sampling for collection of well-aligned dual-energy datasets.
- one of the gratings is moved by a high-precision manipulator such as a piezo-electrical motor for rapid oscillation.
- a high-precision manipulator such as a piezo-electrical motor for rapid oscillation.
- the filter or absorption grating is moved in only a single direction relative to the other grating. This movement can be either in a linear direction or a rotational direction, depending on the embodiment.
- the filter and/or absorption gratings are curved.
- the gratings are concentrically curved, and the moving grating is moved along a correspondingly curved path.
- the gratings are substantially cylindrically shaped. In some embodiments, the gratings are substantially spherically shaped.
- the filter grating includes, in addition to more than one type of filtering region, regions of absorber material interleaved between each filtering region.
- FIG. 1A shows a depiction of kVp-switching X-ray computed tomography (CT).
- FIG. 1B shows a depiction of dual-source detection X-ray CT.
- FIG. 1C shows a depiction of dual-layer scanning X-ray CT.
- FIG. 1D shows a plot of low- and high-energy spectra for kVp-switching X-ray CT.
- FIG. 1E shows a plot of low- and high-energy spectra for dual-source detection X-ray CT.
- FIG. 1F shows a plot of low- and high-energy spectra for dual-layer scanning X-ray CT.
- FIG. 2A shows example filter and absorption gratings that can be used in a system or method according to an embodiment of the subject invention.
- FIG. 2B shows a layout of gratings disposed in front of an X-ray source according to an embodiment of the subject invention.
- FIG. 2C shows a stationary curved absorption grating that can be used according to an embodiment of the subject invention.
- FIG. 2D shows a cross-sectional view of a curved grating having slits designed for a curved geometry according to an embodiment of the subject invention.
- FIG. 2E shows an example filter and absorption gratings according to an embodiment of the invention.
- FIG. 2F shows an example of grating placements relative to an X-ray tube in an exemplary embodiment of the invention.
- FIG. 3A shows an oscillation curve of a filter grating.
- FIG. 3B shows a top view of an absorption grating (left) and a filter grating (right) including two different types of filter (different shadings) according to an embodiment of the subject invention.
- FIG. 3C shows a top view of an absorption grating (left) and a filter grating (right) including two different types of filter (different shadings) according to an embodiment of the subject invention.
- FIG. 3D shows a top view of an absorption grating (left) and a filter grating (right) including two different types of filter (different shadings) according to an embodiment of the subject invention.
- FIG. 3E shows a plot of filter output flux and filter composition vs time for an embodiment of the invention including a stationary absorption grating and a moving filter grating with sinusoidal filter motion.
- FIG. 3F shows a schematic view of a sequence of filter Z-axis positions associated with numbered times in FIG. 3(E) .
- the x-rays flow from left to right with a constant absorption-filter separation, d.
- FIG. 3G shows a schematic view similar to FIG. 3F , but with a reduced absorption-grating duty cycle, achieved at least in part through use of a narrower slit.
- FIG. 4A shows the exposure window for two different types of filters of the same filter grating at a duty cycle of 30%, with the vibration amplitude being half of the filter grating period, according to an embodiment of the subject invention.
- FIG. 4B shows the exposure window for two different types of filters of the same filter grating at a duty cycle of 50%, with the vibration amplitude being half of the filter grating period, according to an embodiment of the subject invention.
- FIG. 4C shows a plot of effective filtration area (filter purity) for a two filter system as a function of absorption grating duty cycle (r).
- FIG. 4F shows a plot of the percentage of the desired filtration (cross-hatched) and flux efficiency (squares) as a function of the absorption-grating duty cycle, r.
- FIG. 5A shows a plot of dual-kVp spectral distributions after grating filtration using an absorption-grating duty cycle of 70%.
- FIG. 5B shows a plot of dual-kVp spectral distributions after grating filtration using an absorption grating duty cycle of 50%.
- FIG. 5C shows a plot of dual-kVp spectral distributions after grating filtration using an absorption grating duty cycle of 30%.
- FIG. 6A shows a lop schematic view of a setup according to an embodiment of the subject invention.
- FIG. 6B shows a top schematic view of a setup according to an embodiment of the subject invention.
- FIG. 6C shows a top schematic view of a setup according to an embodiment of the subject invention.
- FIG. 6D shows a collected CT sinogram.
- FIG. 6E shows an image of collected data for a CT scan.
- FIG. 7A shows a plot of spectral distributions for a two-strip grating.
- FIG. 7B shows a plot of spectral distributions for a multi-strip grating.
- FIG. 8 shows a chest phantom.
- FIG. 9 shows eight reconstructed monochromatic images from a numerical simulation of CT scans.
- FIG. 10 shows eight enlarged images of the local metal areas (the areas around the rods represented by the dots near the lower-middle section of the phantom) of the corresponding images from FIG. 9 .
- FIG. 11 shows eight reconstructed monochromatic images from a numerical simulation of CT scans.
- FIG. 12 shows eight enlarged images of the local metal areas (the areas around the rods represented by the dots near the lower-middle section of the phantom) of the corresponding images from FIG. 11 .
- FIG. 13A shows a plot of signal-to-noise ratio (SNR) for the images of FIG. 9 .
- FIG. 13B shows a plot of SNR for the images of FIG. 11 .
- FIG. 14 shows nine reconstructed monochromatic images from a numerical simulation of CT scans.
- FIG. 15 shows a plot of SNR versus energy for the images of FIG. 14 .
- FIG. 16 shows reconstructed monochromatic images from a numerical simulation of CT scans.
- FIG. 17 shows reconstructed monochromatic images from a numerical simulation of CT scans (top portion) and a plot of SNR versus number of projections.
- FIG. 18 shows four plots for K-edge filtering, with two plots of normalized spectra versus X-ray energy (top portion) and two plots of spectra versus X-ray energy (lower portion).
- FIG. 19 shows an embodiment of planar absorption and filter gratings focused on a source of X-ray radiation.
- FIG. 20 shows the geometric optics for source focal spot blurring of the absorption-grating image at a detector.
- FIG. 21A shows a plot of the flux output and filter type vs time for the arrangement shown in FIG. 21B .
- FIG. 21B shows a schematic view of a sequence of filter Z-axis positions of a vibrating filter grating with interstitial absorbers for the labeled times in FIG. 21A .
- FIG. 22A shows a plot of the flux output and filter type vs time for the arrangement shown in FIG. 22B .
- FIG. 22B shows a schematic view of a filter grating with constant-velocity movement along the Z-axis and source that is constantly on.
- FIG. 23A shows a plot of the flux output and filter type vs time for the arrangement shown in FIG. 23B
- FIG. 23B shows a schematic view of a filter grating with constant-velocity movement along the Z-axis and source that is pulsed.
- FIG. 24 shows a schematic view of the effect of parallax on an embodiment of the present invention in which planar gratings are employed.
- FIG. 25 shows a schematic cross-section view of cylindrically curved gratings in a system according to an embodiment of the invention.
- FIG. 26 shows a schematic view of spherical grating sections flattened to a plane.
- FIG. 27 shows a schematic cross-section view of spherically curved gratings in a system according to an embodiment of the invention.
- FIG. 28A shows simulated experimental data for the detected (distance normalized) x-ray intensity profile across a detector array with and without absorption grating as discussed herein.
- FIG. 28B shows simulated experimental data for the projection seen at the detector with and without the absorption grating for the point spread function (PSF) measured by placing an ideal high-absorption 0.5 mm rod at the center of the imaging field of view.
- PSF point spread function
- FIG. 29A shows the voltage waveform for driving the Kinetic Ceramics A050120 PZT actuator in an embodiment of the invention.
- FIG. 29B shows the current waveform for driving the Kinetic Ceramics A050120 PZT actuator in an embodiment of the invention.
- FIG. 29C shows the power waveform for driving the Kinetic Ceramics A050120 PZT actuator in an embodiment of the invention.
- FIG. 30A shows filter thicknesses for six systems subjected to experimental simulation.
- FIG. 30B shows the contrast-to-noise ratios for the six systems in the simulation referred to in FIG. 30A .
- FIG. 31 shows monochromatic reconstructions for three of the simulations referred to in FIG. 30A .
- Embodiments of the subject invention include systems and method for performing X-ray computed tomography (CT) that can improve spectral separation and decrease motion artifacts without increasing radiation dose to which a patient (e.g., a mammal patient such as a human) or sample is exposed during imaging.
- CT computed tomography
- Systems and methods of embodiments of the subject invention can be used with either a kVp-switching (kilovolt-peak-switching (voltage-alternating)) X-ray source or a single-kVp (non-kVp-switching) X-ray source (e.g., X-ray tube).
- an absorption grating and a filter grating can be disposed between the X-ray source and where a sample/patient to be imaged would be (or is) located (e.g., in front of the X-ray source). Relative motion of the filter and absorption gratings can by synchronized to the kVp switching frequency of the X-ray source (e.g., X-ray tube). Different filter regions can be exposed to X-rays at various time instants, thereby producing low- and high-energy X-rays accordingly.
- a combination of absorption and filter gratings can be used and can be driven in an oscillation movement (relative to each other) that is optimized for a single-kVp X-ray source.
- different filtration materials can be used to generate X-rays in two (or more) energy spectra (one of them at any given time instant).
- only a filter grating alone is required, and the filter grating can be stationary with respect to the X-ray source (e.g., X-ray tube). This stationary approach presents a minimum demand for CT hardware enhancement.
- the filter grating can be just a two-strip filter.
- Dual-energy CT technologies can be classified into the three categories: kVp-switching; dual-layer detection; and dual-source scanning.
- FIGS. 1A-1C are depictions of beams for kVp-switching, dual-source detection, and dual-layer scanning, respectively.
- the kVp-switching method is an X-ray source technology in which low- and high-energy x-ray beams are alternatingly emitted during a scan.
- the dual-layer detector method is based on a detector innovation so that low- and high-energy data are collected in two sensor layers respectively. These two methods both use a single X-ray source to generate dual-energy datasets.
- the resultant low- and high-energy datasets share the same X-ray filter placed in front of the X-ray source, and as a result, the low- and high-energy X-rays are not well separated, as shown in FIGS. 1D and 1E , which are plots for conventional kVp-switching and dual-layer detection, respectively, of low- and high-energy spectra.
- FIGS. 1D and 1E are plots for conventional kVp-switching and dual-layer detection, respectively, of low- and high-energy spectra.
- FIGS. 1D and 1E are plots for conventional kVp-switching and dual-layer detection, respectively, of low- and high-energy spectra.
- FIGS. 1D and 1E are plots for conventional kVp-switching and dual-layer detection, respectively, of low- and high-energy spectra.
- FIG. 1F there are two imaging subsystems. Because the X-ray sources are independent, different X-ray
- dual-source CT systems are more expensive and result in a temporal discrepancy between low- and high-energy data acquisitions. Breathing, heart beating, and patient motion cause artifacts in reconstructed images for related art dual-source systems, compromising material decomposition and monochromatic imaging.
- Embodiments of the subject invention can simultaneously address the spectral overlapping problem with kVp-switching and dual-layer detection systems, as well as the motion artifact problem with a dual-source scanner.
- Grating oriented line-wise filtration (GOLF) systems and methods can enable interlaced filtration patterns for superior energy separation.
- An X-ray filtration device can be easily integrated into a CT scanner and its scanning procedure.
- three main filtration systems-methods can be used, which can be referred to as GOLF k , GOLF c , and GOLF s .
- GOLF k can be used for a kVp-switching X-ray source.
- GOLF k can combine an absorption grating and a filter grating disposed between the X-ray source and where a sample/patient to be imaged would be (or is) located (e.g., in front of the X-ray source).
- GOLF k can synchronize relative motion off the filter and absorption gratings to the kVp switching frequency of the X-ray source (e.g., X-ray tube).
- the filter grating can be driven by a high-precision manipulator, such as a piezo-electrical motor for rapid oscillation of one grating relative to the other. Different filter regions can be exposed to X-rays at various time instants, thereby producing low- and high-energy X-rays accordingly.
- GOLF c and GOLF s can work with a conventional (e.g., non-kVp-switching) X-ray source.
- GOLF c can use a combination of absorption and filter gratings optimized for an X-ray source (e.g., X-ray tube) without kVp-switching.
- the X-ray filter grating and/or the X-ray absorption grating can be driven in an oscillation movement relative to each other, GOLF s only requires a filter grating alone that is stationary with respect to the X-ray source (e.g., X-ray tube). This stationary approach presents a minimum demand for CT hardware enhancement.
- the filter grating can be just a two-strip filter.
- FIG. 2A shows example filter and absorption gratings that can be used in a GOLFk system or method according to an embodiment of the subject invention
- FIG. 2B shows a layout of gratings disposed in front of the X-ray source.
- FIG. 2A shows an X-ray tube with electron beam and anode as the X-ray source, along with two filters making up the filter grating, these are for exemplary purposes only and should not be construed as limiting.
- the absorption grating can be disposed between the X-ray source and the filter grating, and the gratings can be moved relative to each other during operation of the X-ray source.
- the movement of the gratings can be in a direction parallel to the front face of the grating (i.e., in the z-direction as depicted in FIG. 2B ).
- the filter grating can include one filter or a plurality of filters.
- the absorption grating can comprise or be entirely composed of an X-ray absorption material (e.g., gold) to let X-rays go through its open slits only. In this way, the X-rays allowed to go through can be controlled by choosing the width of each slit, the number of slits, the width between slits, and the number of solid portions (non-slits).
- the width of slits and/or solid portions can be uniform across the grating, individually or in total, or such widths can vary.
- the filter grating can spectrally modify the X-ray beam through grating materials.
- the filter grating can include thin metal strips interlacing one or more filtering materials (e.g., two filtering materials).
- the duty cycle of the filter grating can be, for example, 50%, though embodiments are not limited thereto.
- incident X-rays are filtered at different time instants by different kinds of filtering strips.
- a plurality of absorption gratings and/or filter gratings can be used.
- the two gratings can be overlaid in front of the X-ray source, as shown in FIG. 2B .
- the entrance X-rays can alternate at low- and high-energy levels.
- the filter grating can be driven at the same high-frequency relative to the absorption grating.
- the filter grating can oscillate in such a way that the first set of filtering strips happen to be in the X-ray path. Then, for high-energy X-ray imaging, the second set of filtering strips can be exposed to the X-ray source.
- a vibrational GOLF system uses a thin-sheet absorption grating and a thin-sheet filter grating, as shown in FIG. 2E .
- the gratings are overlaid and placed in the x-ray beam at the tube output, as shown in FIG. 2F .
- the absorption grating consists of interlaced bars and open slits, with the bars made of x-ray absorbing material such as Gold so that incident x-rays pass only through the open slits.
- the filter grating consists of interlaced type-1 and type-2 filtering strips with the two types chosen to yield significantly different filtered x-ray spectra.
- the absorption and filter gratings are periodic and matched so that either of the two interlaced filters can be imposed on the entire x-ray beam by shifting the filter grating only one-half period relative to the absorption grating.
- the grating period is smaller than the x-ray source spot size.
- the purpose of the absorption grating is to provide a place for one of the interlaced filters to hide (out of the x-ray beam), while the other filter intersects the x-ray beam.
- FIG. 2F shows the filter grating as the moved grating and places it after the absorption grating on the x-ray path. In other embodiments, however, either grating or both of them can be moved.
- the absorption grating is between the anode and the filter grating, while in other embodiments, the filter grating is between the anode and the absorption grating.
- the gratings can be configured to fit a curved geometry.
- FIG. 2C shows a stationary curved absorption grating
- FIG. 2D shows a cross-sectional view of a grating having slits designed for a curved geometry.
- one or more gratings can be configured to fit a curved geometry, such as for a third generation CT implementation.
- the strips in a curved absorption grating can be aligned according to X-ray emitting angles in a cone geometry, as shown in FIG. 2C .
- the period of the filter grating can be 0.5 mm with a duty cycle of 50%
- the strips in the flat absorption grating can be made of 1 mm gold strips with high X-ray absorption
- the materials of the filter grating are air and 1 mm tin corresponding to low- and high-energy X-ray filtrations, respectively.
- the motion direction of the filter grating can be perpendicular to the longitudinal direction of the filter strips.
- half (or about half) of the original X-rays can be blocked by the absorption grating, and the other half (or about half) can get filtered by the corresponding strips of the filter grating.
- kVp-switching based dual-energy CT the low- and high-energy X-rays are emitted in turn.
- the filter grating vibration frequency can be matched to the X-ray kVp-switching frequency.
- the vibration amplitude can be optimized according to the duty cycle of the absorption grating. With the duty cycle being 1 ⁇ 2r, the optimized vibration amplitude is
- FIG. 3A shows an oscillation curve of a filter grating according to an embodiment.
- the oscillation period is equal to half the time interval between two adjacent X-ray projections in the kVp-switching CT scan.
- FIGS. 3B-3D show top views of an absorption grating (left) and a filter grating (right) including two different types of filter (different shadings).
- An ideal X-ray filtration setting is shown in FIG. 3C , in which the absorption grating and the filter grating are in a perfect alignment without filter materials mixed in the x-ray beam. Referring to FIG.
- the filter grating can be aligned such that one of its filter materials matches up with each slit of the absorption grating.
- the absorption grating and the filter grating are in relative motion, and the X-rays are filtered by two filters with a changing material mixture, for example leading to the orientation shown in FIG. 3B at certain times.
- FIG. 3D shows an example absorption grating with a narrower grating opening. Referring to FIG. 3D , the configuration with a narrower opening minimizes the problems that may be caused by mixed filtration, but this can come at a cost of reduced photon efficiency.
- FIGS. 3B and F show how some embodiments of the present technology operate when the absorption grating 103 is stationary and the filter grating 102 is moved.
- FIG. 3E shows a plot of the flux output and filter composition vs time, where sinusoidal displacement of the filter grating is used.
- the filter grating has two sets of filter regions 100 and 101 .
- FIG. 3F shows relative Z-dimension (vertical) positions of the absorption and filter gratings associated with numbered times in FIG. 3E (points 1 - 9 ).
- the filter moves only in the Z direction, while the distance between the absorption and filter gratings, d, is held constant as in position 1 .
- the first filter 100 is x-rays low-pass, and the second filter 101 is high-pass.
- position 3 all x-rays that pass the absorption grating are low-pass filtered, while at position 7 , all x-rays are high-pass filtered.
- the output x-ray spectrum is a mix of respectively low- and high-passed low and high kVp spectra. Integration of the x-ray flux occurs over the detector view period, aid the changing spectra yields spectral blur and reduced high and low spectral separation.
- maximum separation of the two GOLF output spectra is achieved by setting the filter displacement frequency to one-half of the detector view rate and aligning filter positions 1 and 5 with the start of low-kVp and high-kVp views, respectively.
- the absorption and filter gratings have the same spatial period, their duty cycles are both 50%, and the peak-to-peak filter displacement is 1 ⁇ 2 period.
- other duty cycles and peak-to-peak displacements are employed in other embodiments.
- Some kVp-switching systems may use longer view periods for the low-energy spectra and shorter ones for the high-energy spectra because x-ray tubes generate much less x-ray flux at low voltage than they do at high voltage for the same anode current.
- some embodiments of the present invention include lengthened low-pass filter exposure and shortened high-pass exposure. View asymmetry in such embodiments can be accommodated by increasing the filter low-pass duty cycle from 50% and decreasing the absorption-grating duty cycle.
- FIG. 3G further shows that, in some embodiments of the invention, spectral blur resulting from a sinusoidal filter motion can be reduced by decreasing the absorption-grating duty cycle.
- FIG. 3G shows an embodiment similar to that in FIG. 3E-3F , but with a significantly reduced absorption-grating duty cycle.
- the filter grating and its sinusoidal peak-to-peak motion are unchanged in this embodiment.
- the filter edges spend less time traversing the slits, meaning that each detector view period gets more time with correctly filtered x-ray flux.
- the absorption-grating output flux is directly proportional to the absorption grating duty cycle. Therefore, reducing the absorption grating duty cycle improves spectral separation at the cost of the total output flux.
- FIGS. 4A-4B show the exposure window for two different types of filters of the same filter grating at duty cycles of 30% and 50%, respectively, for the vibration amplitude being half of the filter grating period.
- FIG. 4C shows a plot of effective filtration area as a function of absorption grating duty cycle (r).
- FIGS. 4A-4C are all for a GOLF k system/method according to an embodiment of the subject invention. Referring to FIGS. 4A and 4B , within the exposure window ⁇ t, Filters 1 and 2 are gradually exposed through the absorption grating opening, in which Filter 1 offers the correct filtration, while Filter 2 introduces a contamination. Referring to FIG. 4C , by increasing the open ratio to 1, the filtration method is degraded to the conventional kVp-switching method.
- FIGS. 4C-4E show how the absorption-grating duty cycle, r, affects the amount of spectral mixing during a view-period for the embodiment represented in FIG. 3G .
- S T (E) be the energy-dependent (E) tube output spectrum during the view
- F c (E) be the desired filter energy function
- F w (E) the undesired filter energy function.
- C(t) depends only on the filter-motion as a function of time, which in this case is sinusoidal.
- S a ( E ) S T ( E )[ F c ( E ) A eff +F w ( E )(1 ⁇ A eff )], (1)
- a eff 1 ⁇ ⁇ ⁇ T ⁇ ⁇ 0 ⁇ ⁇ ⁇ T ⁇ C ⁇ ( t ) ⁇ dt . ( 2 )
- FIGS. 5A-5C show plots of spectral distributions for a GOLF k system/method according to an embodiment of the subject invention, at absorption grating duty cycles of 70%, 50%, and 30%, respectively.
- vertical dotted lines indicate corresponding mean energies (also labeled on the plots), and in each of these plots, the left-most plotted line is for an energy of 80 kVp end the right-most plotted line is for an energy of 140 kVp.
- the plots in FIGS. 5A-5C assume air and 1 mm tin as two filtering materials in the filter grating. Referring to FIGS.
- a narrower absorption grating opening results in better separation of the spectra; though, a narrow absorption grating opening can decrease the X-ray efficiency.
- the output spectra (pre-patient) are calculated using Eqs. (1) and (2) above.
- the low and high-pass filter materials are Air and 0.5 mm of Tin, respectively.
- the filter blurring can be avoided without having to reduce the absorption grating duty cycle.
- the x-ray source is rapidly pulsed during any view period. By properly phasing the source pulses with the filter positions, both the spectral separation and the flux efficiency of such embodiments can be improved. For example, staying with the 50% absorption grating in FIG. 3E , the source can be turned on at times 2 and 6 , and turned off at times 4 and 8 . This generates x-rays and illuminates the absorber slits only when the filter is mostly of one type.
- the gratings are each a single continuous grating (not segmented), and the moved grating is planar and moved only in the plane.
- Gratings used in embodiments of the technology are designed to work with the large fan and cone angles of a CT system and, because the gratings have a significant thickness, they are “focused” on the source spot to avoid flux loss and spectral error.
- the stationary grating is curved, in other embodiments both gratings are planar and very close together to minimize alignment issues.
- FIG. 19 illustrates an embodiment of planar absorption and filter gratings focused on a focal spot.
- the absorber and filter grating periods must be properly related for the given grating separation, d.
- the periods are nearly equal.
- the filter grating will remain in focus when it is shifted (vibrated) by only the required 1 ⁇ 2 period.
- the absorber and filter materials and thicknesses are chosen to provide the required absorption and spectral filtration for the given source spectra. In an embodiment with a gold absorber for 80 and 140 kVp source spectra, a gold thickness of 0.5 mm would be sufficient to block at least 98% at all energy below 140 keV. In an embodiment with Air and Tin as filters, a filter-grating thickness of 0.5 mm will provide good spectral separation improvement.
- the grating period must be small enough to allow the rapid filter displacement but not so small that the grating cannot be fabricated or mechanically stabilized. Furthermore, it must not be too large relative to the source-spot size because the absorption grating bars would cast undesirable non-uniform (pixel-location-dependent) shadows on the detector (although they can be corrected), or for very large bars, completely block some detector pixels.
- FIG. 20 shows the source spot, absorption grating and detector relevant geometry.
- the extended spot size will beneficially blur the image of the grating on the detector in some embodiments and the grating period can be chosen to insure little or no grating visibility in the detector image. Grating-induced flux variation across the defector is avoided if the focal-spot size F S , the source-to-grating distance SGD, the source-to-detector distance SDD, and the absorber grating period ⁇ A are related by
- n 1 n ⁇ F S ⁇ ( 1 - SGD SDD ) ( 3 )
- n is a positive integer.
- Eq. (3) every detector pixel gets the same percentage of flux blocked by the grating. That is, if Eq. (3) is satisfied and the grating duty cycle of 50% is used, then exactly 1 ⁇ 2 of the focal spot is blocked by the absorption grating for every point on the detector.
- Eq. (3) is not satisfied, there is grating-induced flux variation across the detector array. As the integer n grows larger, the grating-induced variations diminish even when Eq. (3) is net satisfied. If necessary, this variation could be allowed to remain and be accounted in the common CT air and spectral calibrations.
- the GOLF gratings are to be placed close to the source but outside of the x-ray tube (in other embodiments, they are in the x-ray tube), and an additional 10 mm to get SGD ⁇ 75 mm.
- FIG. 21A shows a plot of the filter Z position and filter type vs time for the filter grating movement and relationship to the X-ray beam shown schematically in FIG. 21B .
- FIG. 21B shows the numbered grating positions that correspond to the numbered points along the curve plotted in FIG. 21A .
- the absorbers placed between the different filter stripes allow only one filter type to be active in any absorber-grating slit at a time.
- the slits in the absorber grating must not be larger than the absorbers in the filter grating.
- flux efficiency of 15.9% when the absorber-grating duty cycle is 25% is achieved in some embodiments.
- a set of absorbing regions 105 are positioned between each neighboring, alternating filter region 100 , 101 .
- the set of filter regions 100 of the first type e.g., low-pass filter regions
- the absorbers 105 are positioned between each individual filter region.
- each of the two sets of filter regions produce different X-ray spectra from the X-ray radiation.
- This embodiment also includes a Tin filter grating that is 0.5 mm thick, has a 50% duty cycle and 0.244 mm period, and is located 75 mm from the source spot.
- the filter grating is vibrated with a peak-to-peak (p-p) amplitude of one half of the grating period, or ⁇ 120 um at a 1 kHz rate.
- This embodiment includes a Kinetic Ceramics A050120 PZT actuator, which provides a maximum displacement of 120 um when 1000 V is applied. It has a self-resonant frequency of 12.3 kHz and, with light loading, it supports 1 kHz sinusoidal operation with 120 um p-p displacement.
- the forces required to vibrate the filter grating are calculated as follows, if the filter is placed 75 mm from the source in a 64-slice CT machine with a fan angle of 57 degrees and a cone angle of 4 degrees, then the filter grating must be approximately 82 mm in X and 6 mm in Z to filter the entire beam.
- the filter volume is then 246 mm 3 , half Air and half Tin. With the density of Tin at 7.31 g/cm 3 , the resulting mass is only 0.9 grams. Providing another ⁇ 10 ⁇ mass for filter stiffening/stability, the mass to be vibrated is ⁇ 10 grams.
- D peak 60 um so that the peak acceleration is 2.4E+03 m/s 2 .
- the peak force required for this acceleration of ⁇ 10 grams is 24 Newtons. This is very small compared to the actuator blocking force of 4500 N (Newtons) such that the actuator can achieve the desired 120 um of displacement at ⁇ 1000 V.
- V ⁇ ( t ) 500 ⁇ D peak 120 ⁇ [ 1 + sin ⁇ ( 2 ⁇ ⁇ ⁇ ⁇ ft ) ] ( 8 )
- I ⁇ ( t ) 2500 ⁇ ⁇ CfD peak 120 ⁇ cos ( 2 ⁇ ⁇ ⁇ ft ) ( 9 )
- steps are taken to prevent the vibration from coupling to other CT system components (the tube, etc.) and/or making offensive audible noise.
- One method to reduce unwanted coupling is to incorporate a counter-weight in the GOLF module so the net momentum of the GOLF module is zero, in some embodiments, the absorption grating makes an effective counter weight.
- a parallel stiffening plate, captivating travel tracks, and mode dampening methods are used in some embodiments to avoid travelling waves and/or out of plane vibrations within the grating. While some embodiments use linear grating slits and bars, other embodiments use a checkerboard grating to reduce unwanted vibration modes by reducing long unsupported regions of absorbing bars within the grating.
- a planar filter grating is used that is longer than the x-ray beam footprint in one dimension, and the grating is slid at a constant speed in that one dimension during a scan.
- the part of the filter grating that is interacting with the x-ray radiation is moved in substantially only one direction during operation of the source.
- the only one direction is a linear dimension. In other embodiments, such as some described below, the only one direction is rotation about an axis.
- FIG. 22 shows a schematic representation of an embodiment in which a constant-velocity sliding filter grating is employed and a source that is constantly on.
- the gratings in this embodiment shown in FIG. 22B are the same as those employed in the embodiment shown in FIG. 21B , but the constant velocity yields the triangular flux output function shown in FIG. 22A .
- the filter grating is moved toward the top of the page of FIG. 22 (increasing Z).
- the sliding motion is synchronized with the detector view rate so that filtration alternates view by view.
- the filter grating is both periodic and focused at infinity so that, from the source point of view, all integer period translations are indistinguishable.
- the grating filter is slid in the Z (cone angle) direction because, with CT, this direction has the least angle change across the beam footprint.
- the maximum flux efficiency for this embodiment is 12.5% with a source that is constantly on.
- FIG. 23 shows a schematic view of a constant motion grating used with a pulsed source.
- half of the flux waste associated with the triangle slopes in FIG. 22A can be eliminated as shown in FIG. 23 .
- the source is enabled only while a single filter type spans all absorber-grating slits. This helps maintain spectral purity even in the absence of interstitial filter absorbers present in other embodiments. Flux efficiency for this embodiment is 25%.
- a flexible filter grating “tape” is used.
- the filter grating is moved relative to, and in some cases across, the absorption grating and is collected on reels, similar to traditional flexible film used for movies.
- the flexible filter grating is attached to a reel, which is driven by an actuator or motor to take up the flexible filter grating at the desired speed. The portion of the grating that interacts with the x-ray radiation will thereby move in a single direction relative to the absorption grating while the source is in operation.
- the absorption grating is moved relative to the filter grating. Similarly, the absorption grating is moved in only a single direction in some embodiments, in ways similar to those discussed above with respect to the filter grating.
- FIG. 24 shows an schematic view illustrating the effect of parallax encountered at large cone angles with embodiments of the invention that utilize “planar” gratings, including single direction sliding GOLF systems.
- Parallax causes extra flux loss that can be accounted in CT calibration, but large parallax could completely block all x-rays.
- the flux loss can be reduced by increasing the grating period while holding the filter thickness constant.
- curved gratings are used.
- cylindrically curved absorption and filter gratings are used, as shown in FIG. 25 .
- the axis of the cylinder is a line containing the source point and is parallel to the fan (x) direction, which extends into and out of the page.
- the absorption-grating and filter-grating edges are axially oriented, such that the gratings are in focus across the entire beam footprint.
- the curvature of the absorption grating and the curvature of the filter grating are concentric to each other with respect to the x-ray source.
- the filter grating is rigid and slid around the curved movement path.
- the filter grating is flexible and uses reels in a manner similar to the manner described above.
- the flexible filter grading is slid against the curved stationary absorber grating.
- Some embodiments using curved gratings use a pulsed source to improve the flux efficiency, as shown in FIG. 23 .
- Embodiments with curved gratings help address the issue of the effect of parallax. As a result, the grating period can be made smaller to allow for shorter sliding travel in such embodiments.
- FIG. 25 also shows the use of interstitial absorber regions in the curved filter grating, which function in a manner similar to that described above with respect to interstitial absorbers in planar gratings.
- FIGS. 26 and 27 Another alternative embodiment utilizes spherically curved gratings.
- a spherically shaped stationary absorber-grating section and a relatively slowly rotating spherically shaped filter-grating section are used, as shown in FIGS. 26 and 27 .
- FIG. 26 shows a surface view of the two grating sections flattened to disks for illustration.
- FIG. 27 shows a side view of how the spherical sections are positioned relative to the source in this embodiment.
- the two gratings are radially oriented with a constant angular grating period and overlaid with their radial centers aligned. Only the filter section is rotated, and its center of rotation is placed outside the beam footprint, in this embodiment.
- the absorber and filter spherical sections use a radial checkerboard pattern, where the absorber and filter grating patterns in FIG. 26 are divided into separate rings, and the rings are phase-shifted relative to each other.
- FIG. 26 shows a filter grating with interstitial absorbers for improved spectral purity, but, in other embodiments, the interstitial absorbers are not used so as to increase the flux efficiency where a pulsed source is used.
- the description above in connection with FIGS. 22 and 23 are also applicable to embodiments in which grating rotation is used.
- One key advantage for spherical, rotating gratings is that all points on the absorber and filter gratings are in focus (no parallax) in some embodiments.
- SOD source-to-grating distance
- the angular grating period should then be chosen small enough for acceptably low grating image visibility from any part of the grating in the x-ray beam.
- the size of the rotating filter is described by the spherical angle it spans, and it is desirable to choose a size that has acceptable grating slit widths.
- ⁇ Fmin 0.122 at the edge of the footprint closest to the filter rotation center.
- the spherical gratings are portions of hemispheres—that is, less than half a sphere.
- the size of the sections is chosen to work with the particular system or CT machine at issue.
- the rotating grating rotates about an axis that runs from approximately the location of the x-ray source to the approximate center of the spherical grating section.
- the use of spherically curved gratings is another embodiment in which one of the gratings is moved in only a single direction relative to the other grating (i.e., one of clockwise or counterclockwise rotation of a grating).
- the filter grating is rotated.
- the absorber grating is rotated.
- a grating is rotated back and forth between two rotational directions.
- FIGS. 6A-6C show top schematic views of a GOLF c setup according to various embodiments of the subject invention.
- the X-ray sources shown in FIGS. 6A-6C are for exemplary purposes only and should not be construed as limiting.
- a degraded grating filter can include only two filter strips, one of which is low-absorption material (e.g., air or aluminum) and the other is a high-absorption material (e.g., tin).
- the low-absorption material can keep the original X-ray beam while the high-absorption material can harden the X-ray beam (see also FIGS. 6A-6C ).
- FIG. 6D shows the collected CT sinogram, in which the let side is low mean-energy data, and the other side high mean-energy data, which are for low-energy and high-energy image reconstruction, respectively.
- a penumbra can be seen along the middle line of the sinogram, as marked by the (red) arrow in FIG. 6D , which will influence the image reconstruction.
- relative displacement between the X-ray focal spot and filter grating can be introduced. It can be implemented, for example, via e-beam control in the X-ray tube (the flying focal spot method) or filter oscillation outside the X-ray source; these two methods are equivalent in principle.
- the low- and high-absorption materials can be 0.1-mm and 1.0-mm tin materials, respectively, and the size of the X-ray focal spot can be 1 mm.
- the penumbra in the detector plane is about 8 mm in width under the imaging geometry of a system in which the filter is 10 cm away from the X-ray focal spot.
- FIGS. 7A and 7B show plots of spectral distribution for a GOLF c setup for a two-strip grating and a multi-strip (more than two-strip) grating, respectively, according to an embodiment of the subject invention.
- the two types of filtering materials were 0-mm titanium (air) and 1.0-mm titanium materials.
- vertical dotted lines indicate corresponding mean energies (also labeled on the plots), and in each of these plots, the right-most plotted line is for 1.0 mm tin (50% duty cycle in FIG. 7B ).
- FIG. 7A and 7B show plots of spectral distribution for a GOLF c setup for a two-strip grating and a multi-strip (more than two-strip) grating, respectively, according to an embodiment of the subject invention.
- the two types of filtering materials were 0-mm titanium (air) and 1.0-mm titanium materials.
- vertical dotted lines indicate corresponding mean energies (also labele
- the left-most plotted line is for 0.1 mm tin
- the left-most plotted line is for 0.0 mm tin at 50% duty cycle.
- the two-strip filter can be replaced by a grating comprising alternating strips, coupled with an absorption grating as described with reference to GOLF k .
- the relative displacement between the X-ray focal spot and the filter grating is not needed because the motion of the absorption grating defines the filtration for the X-ray beam.
- the drawback of the grating method is its low X-ray flux efficiency.
- FIG. 7B is based on a multi-strip grating including 0-mm titanium (air) and 1.0-mm titanium materials with a duty cycle of 50%.
- the GOLF c systems and methods described herein can be used with a conventional X-ray source that does not include kVp-switching, thereby relaxing the need for a kVp-switching X-ray source.
- dynamic relative grating displacement can stall be used to select X-ray filtration effects.
- the dual-energy imaging system can be further simplified with a stationary filtering grating alone or just a stationary two-strip filter where an X-ray imaging model is necessary to separate mixed spectra for hybrid imaging reconstruction (see also, e.g., reference [22] in the References section, which is hereby incorporated herein by reference in its entirety).
- the stationary filtering grating methods can be referred to as “GOLF s ”.
- a monochromatic image can be reconstructed in both the projection and image domains (see, e.g., references [8] and [23] in the References section, both of which are hereby incorporated herein by reference in their entireties). This is based on the assumption that any material can be represented as a linear combination of two basis materials:
- Systems and method of embodiments of the subject invention in combination with single-kVp imaging and kVp-switching technology, open new doors to extract dual energy data effectively, with flexibility, and improved cost-effectiveness.
- the key feature of dual-energy CT imaging is the spectral separation that helps avoid spectral mixing and reveals more information regarding material composition and monochromatic imaging.
- Systems and method of embodiments of the subject invention can take advantage of these attributes of dual-energy CT imaging while also addressing the motion artifact problem with a dual-source scanner and the spectral overlapping problem with kVp-switching and dual-layer detection systems.
- GOLF k performs the best in terms of spectral separation, and a combination of absorption grating(s) and filter grating(s) can be used with a single-source CT system to achieve dual-source, dual-energy CT performance similar to that in a GOLF c system/method.
- a GOLF c or GOLF s system/method can be used to significantly improve spectral separation.
- GOLF s can be thought of as the simplest case of GOLF c with the highest photon utilization.
- GOLF s can work in a stationary mode with only one filter grating, for example in a full scan.
- the image reconstruction algorithm for GOLF s can be based on a non-linear X-ray data generation model.
- Embodiments of the subject invention can include dynamically modulating the filter grating of millimeter-/sub-millimeter-sized filtering strips by a matching absorption grating with a small oscillation amplitude at a high frequency. Due to this micro-technology, the medical CT requirements for full coverage over the field of view and a rapid change in filtration settings can be simultaneously achieved to yield superior spectral filtration.
- the filter vibration can be driven by, for example, a piezo-electrical device, which is a mature technology compatible with CT scanning. The same is true for embodiments involving translation (in a single direction during source operation) or rotation of the filter and/or absorption grating.
- the use of an absorption grating does result in the loss of some X-ray flux from the source.
- the patient e.g., a mammal such as a human
- embodiments that use a pulsed x-ray source are desirable, since this can cut wasted flux in half.
- the absorption grating does not increase the patient radiation dose.
- Some embodiments of the invention increase spectral separation and CNR/dose ratio of kVp switching to that of the state of the art dual-source CT system while avoiding dual-source system cost and temporal mismatch issues.
- a filter grating can be used with no absorption grating, thereby not completely blocking the path of any X-rays.
- the image reconstruction from data collected with GOLF s can be more complicated, involving non-linear data modeling and compressed sensing (see also reference [22] from the References section, which is hereby incorporated herein by reference in its entirety). Spectral mixing in multiple penumbras could be an issue.
- the gratings can be made in 2D instead of 1D (e.g., to fit into cone-beam geometry).
- more than two filtering material types can be introduced (e.g., for multi-energy x-ray imaging).
- X-ray path lengths in the patient body can be taken into account so that the final diagnostic performance can be optimized instead of the spectral separation itself, which is an indirect measure anyway.
- Embodiments of the subject invention can advantageously be used with existing X-ray CT systems with minimal overhead expense. Piezoelectric devices and narrow grating period allow embodiments of vibrational GOLF systems to be implementable with the high oscillation frequency needed for modern single-source CT scanners.
- the imaging performance can be improved significantly in terms of monochromatic image quality, material decomposition, and radiation dose reduction.
- absorption grating can decrease the efficiency of the X-ray source, patient radiation dose is not increased, so this is not a major drawback.
- the methods and processes described herein can be embodied as code and/or data.
- the software code and data described herein can be stored on one or more machine-readable media (e.g., computer-readable media), which may include any device or medium that can store code and/or data for use by a computer system.
- machine-readable media e.g., computer-readable media
- the computer system and/or processer When a computer system and/or processer reads and executes the code and/or data stored on a computer-readable medium, the computer system and/or processer performs the methods and processes embodied as data structures and code stored within the computer-readable storage medium.
- computer-readable media include removable and non-removable structures/devices that can be used for storage of information, such as computer-readable instructions, data structures, program modules, and other data used by a computing system/environment.
- a computer-readable medium includes, but is not limited to, volatile memory such as random access memories (RAM, DRAM, SRAM); and non-volatile memory such as flash memory, various read-only-memories (ROM, PROM, EPROM, EEPROM), magnetic and ferromagnetic/ferroelectric memories (MRAM, FeRAM), and magnetic and optical storage devices (hard drives, magnetic tape, CDs, DVDs); network devices; or other media now known or later developed that is capable of storing computer-readable information/data.
- volatile memory such as random access memories (RAM, DRAM, SRAM
- non-volatile memory such as flash memory, various read-only-memories (ROM, PROM, EPROM, EEPROM), magnetic and ferromagnetic/ferroelectric memories (MRAM, FeRAM), and magnetic and optical
- Computer-readable media should not be construed or interpreted to include any propagating signals.
- a computer-readable medium of the subject invention can be, for example, a compact disc (CD), digital video disc (DVD), flash memory device, volatile memory, or a hard disk drive (HDD), such as an external HDD or the HDD of a computing device, though embodiments are not limited thereto.
- a computing device can be, for example, a laptop computer, desktop computer, server, cell phone, or tablet, though embodiments are not limited thereto.
- the subject invention includes, but is not limited to, the following exemplified embodiments.
- Embodiment 1 A system for performing X-ray computed tomography (CT) imaging, the system comprising:
- a filter grating disposed between the source and the detector (to modify the original X-ray energy spectrum of the X-ray radiation of the X-ray source into two or more spectra), wherein the filter grating is positioned closer to the source than the detector is;
- an absorption grating aligned with the filter grating (either before the filter grating or after the filter grating, along a path of X-ray radiation from the source to the detector) (to selectively block at least a portion of the X-ray radiation from reaching the filter grating so that a preferred X-ray spectrum can pass through the filter grating and can go through a patient or subject to be imaged at a given time instant),
- At least one of the absorption grating and the filter grating is configured to move relative to the other during operation of the source.
- Embodiment 2 The system according to embodiment 1, wherein the source is a kVp-switching X-ray source.
- Embodiment 3 The system according to embodiment 2, wherein the absorption grating and the filter grating oscillate relative one another, and the oscillation is synchronized with a switching frequency of the source, such that each time the source switches its voltage level, at least one of the absorption grating and the filter grating moves relative to the other.
- Embodiment 4 The system according to any of embodiments 2-3, wherein an oscillation period of the relative movement between the gratings is equal to half a time interval between two adjacent X-ray projections of the source.
- Embodiment 5 The system according to embodiment 1, wherein the source is a single-kVp X-ray source (non-kVp-switching X-ray source).
- Embodiment 6 The system according to embodiment 5, wherein the relative movement of the gratings is an oscillation movement (relative to each other) that is optimized for the single-kVp X-ray source.
- Embodiment 7 The system according to any of embodiments 1-6, wherein the filter grating comprises at least two different types of filter material.
- Embodiment 8 The system according to any of embodiments 1-7, wherein the filter grating comprises exactly two different types of filter material.
- Embodiment 9 The system according to any of embodiments 1-8, wherein the absorption grating comprises slit portions and solid portions disposed alternatingly.
- Embodiment 10 The system according to embodiment 9, wherein a width of each slit portion of the absorption grating is the same as that of each other slit portion of the absorption grating.
- Embodiment 11 The system according to any of embodiments 9-10, wherein a width of each solid portion of the absorption grating is the same as that of each other solid portion of the absorption grating.
- Embodiment 12 The system according to any of embodiments 9-11, wherein a width of each slit portion of the absorption grating is the same as that of each solid portion of the absorption grating.
- Embodiment 13 The system according to any of embodiments 9-11, wherein a width of at least one slit portion of the absorption grating is different from that of al least one solid portion of the absorption grating.
- Embodiment 14 The system according to any of embodiments 9-11, wherein a width of at least one slit portion of the absorption grating is narrower than that of at least one solid portion of the absorption grating.
- Embodiment 15 The system according to any of embodiments 9-11, wherein a width of at least one slit portion of the absorption grating is wider than that of at least one solid portion of the absorption grating.
- Embodiment 16 The system according to any of embodiments 9-11, wherein a width of each slit portion of the absorption grating is narrower than that of at least one solid portion of the absorption grating.
- Embodiment 17 The system according to any of embodiments 9-11, wherein a width of each slit portion of the absorption grating is wider than that of at least one solid portion of the absorption grating.
- Embodiment 18 The system according to any of embodiments 9-11, wherein a width of each slit portion of the absorption grating is narrower than that of each solid portion of the absorption grating.
- Embodiment 19 The system according to any of embodiments 9-11, wherein a width of each slit portion of the absorption grating is wider than that of each solid portion of the absorption grating.
- Embodiment 20 The system according to any of embodiments 9-11, wherein a width of at least one slit portion of the absorption grating is narrower than that of each solid portion of the absorption grating.
- Embodiment 21 The system according to any of embodiments 9-11, wherein a width of at least one slit portion of the absorption grating is wider than that of each solid portion of the absorption grating.
- Embodiment 22 The system according to any of embodiments 1-21, wherein the relative motion between the absorption grating and the filter grating is in a direction parallel to a from face of the absorption grating facing the source.
- Embodiment 23 The system according to any of embodiments 1-22, wherein the absorption grating comprises a metal.
- Embodiment 24 The system according to any of embodiments 1-23, wherein the absorption grating comprises gold.
- Embodiment 25 The system according to any of embodiments 1-24, wherein a thickness of the absorption grating is 1 mm.
- Embodiment 26 The system according to any of embodiments 1-24, wherein a thickness of the absorption grating is at least 1 mm.
- Embodiment 27 The system according to any of embodiments 1-24, wherein a thickness of the absorption grating is no more than 1 mm.
- Embodiment 28 The system according to any of embodiments 1-24, wherein a thickness of the absorption grating is 0.5 mm.
- Embodiment 29 The system according to any of embodiments 1-24, wherein a thickness of the absorption grating is at least 0.5 mm.
- Embodiment 30 The system according to any of embodiments 1-24, wherein a thickness of the absorption grating is no more than 0.5 mm.
- Embodiment 31 The system according to any of embodiments 1-30, wherein the filter grating comprises a first filter material and a second filter material that is less dense than the first filter material.
- Embodiment 32 The system according to embodiment 31, wherein the first filter material is a metal air and the second filter material is air.
- Embodiment 33 The system according to any of embodiments 31-32, wherein the first filter material is tin.
- Embodiment 34 The system according to any of embodiments 31-33, wherein the filter grating comprises a plurality of strips of the second filter material, with the first filter material disposed alternatingly with the plurality of strips of the second filter material.
- Embodiment 35 The system according to any of embodiments 1-34, wherein a thickness of the filter grating is 1 mm.
- Embodiment 36 The system according to any of embodiments 1-34, wherein a thickness of the filter grating is at least 1 mm.
- Embodiment 37 The system according to any of embodiments 1-34, wherein a thickness of the filter grating is no more than 1 mm.
- Embodiment 38 The system according to any of embodiments 1-34, wherein a thickness of the filter grating is 0.5 mm.
- Embodiment 39 The system according to any of embodiments 1-34, wherein a thickness of the filter grating is at least 0.5 mm.
- Embodiment 40 The system according to any of embodiments 1-34, wherein a thickness of the filter grating is no more than 0.5 mm.
- Embodiment 41 The system according to any of embodiments 1-40, wherein the filter grating moves while the absorption grating stays stationary during operation of the source.
- Embodiment 42 The system according to any of embodiments 1-40, wherein the absorption grating moves while the filter grating stays stationary during operation of the source.
- Embodiment 43 The system according to any of embodiments 1-40, wherein both the absorption grating and the filter grating move during operation of the source.
- Embodiment 44 The system according to any of embodiments 1-43, further comprising a motor configured to move at least one of the absorption grating and the filter grating relative to the other during operation of the source.
- Embodiment 45 The system according to embodiment 44, wherein the motor is a piezo-electrical motor.
- Embodiment 46 The system according to any of embodiments 1-45, wherein the absorption grating has a curved geometry.
- Embodiment 47 The system according to any of embodiments 1-46, wherein the filter grating has a curved geometry.
- Embodiment 48 The system according to any of embodiments 1-47, wherein the filter grating is disposed between the source and a patient to be imaged.
- Embodiment 49 The system according to any of embodiments 1-48, wherein a distance between the filter grating and the source is less than 1 meter.
- Embodiment 50 The system according to any of embodiments 1-48, wherein a distance between the filter grating and the source is less than 500 mm.
- Embodiment 51 The system according to any of embodiments 1-48, wherein a distance between the filter grating and the source is less than 250 mm.
- Embodiment 52 The system according to any of embodiments 1-51, wherein the source is an X-ray tube.
- Embodiment 53 A method of performing X-ray CT imaging, the method comprising:
- Embodiment 54 The method according to embodiment 53, wherein the filter grating moves while the absorption grating stays stationary during operation of the source.
- Embodiment 55 The method according to embodiment 53, wherein the absorption grating moves while the filter grating stays stationary during operation of the source.
- Embodiment 56 The method according to embodiment 53, wherein both the absorption grating and the filter grating move during operation of the source.
- Embodiment 57 The method according to any of embodiments 53-56, wherein the source is a kVp-switching X-ray source, and wherein an oscillation period of the relative movement between the gratings is equal to half a time interval between two adjacent X-ray projections of the source.
- Embodiment 58 The method according to any of embodiments 53-56, wherein the source is a single-kVp X-ray source, and wherein the relative movement of the gratings is an oscillation movement (relative to each other) that is optimized for the single-kVp X-ray source.
- Embodiment 59 The method according to any of embodiments 53-58, wherein the patient is a mammal.
- Embodiment 60 The method according to any of embodiments 53-59, wherein the patient is a human.
- Embodiment 61 A system for performing X-ray computed tomography (CT) imaging, the system comprising:
- a filter grating disposed between the source and the detector (to modify the original X-ray energy spectrum of the X-ray radiation of the X-ray source into two or more spectra), wherein the filter grating is positioned closer to the source than the detector is,
- the filter grating is configured to be stationary during operation of the source.
- Embodiment 62 The system according to embodiment 61, wherein the filter grating comprises at least two different types of filter material.
- Embodiment 63 The system according to any of embodiments 61-62, wherein the filter grating comprises exactly two different types of filter material.
- Embodiment 64 The system according to any of embodiments 61-63, wherein the filter grating comprises at least two filter strips.
- Embodiment 65 The system according to any of embodiments 61-63, wherein the filter grating comprises exactly two filter strips.
- Embodiment 66 The system according to embodiment 65, wherein the two filter strips comprise a first filter strip of a first filter material and a second filter strip of a second filter material different from the first filter material.
- Embodiment 67 The system according to embodiment 66, wherein the first filter material is a metal air and the second filter material is air.
- Embodiment 68 The system according to any of embodiments 66-67, wherein the first filter material is tin.
- Embodiment 69 The system according to any of embodiments 61-64, wherein the filter grating comprises a first filter material and a second filter material that is less dense than the first filter material.
- Embodiment 70 The system according to embodiment 69, wherein first filter material is a metal and the second filter material is air.
- Embodiment 71 The system according to any of embodiments 69-70, wherein the first filter material is tin.
- Embodiment 72 The system according to any of embodiments 69-71, wherein the first and second filter materials are disposed alternatingly in the filter grating.
- Embodiment 73 The system according to any of embodiments 61-72, wherein a thickness of the filter grating is 1 mm.
- Embodiment 74 The system according to any of embodiments 61-72, wherein a thickness of the filter grating is at least 1 mm.
- Embodiment 75 The system according to any of embodiments 61-72, wherein a thickness of the filter grating is no more than 1 mm.
- Embodiment 76 The system according to any of embodiments 61-72, wherein a thickness of the filter grating is 0.5 mm.
- Embodiment 77 The system according to any of embodiments 61-72, wherein a thickness of the filter grating is at least 0.5 mm.
- Embodiment 78 The system according to any of embodiments 61-72, wherein a thickness of the filter grating is no more than 0.5 mm.
- Embodiment 79 The system according to any of embodiments 61-78, wherein the filter grating has a curved geometry.
- Embodiment 80 The system according to any of embodiments 61-79, wherein the filter grating is disposed between the source and a patient to be imaged.
- Embodiment 81 The system according to any of embodiments 61-80, wherein a distance between the filter grating and the source is less than 1 meter.
- Embodiment 82 The system according to any of embodiments 61-80, wherein a distance between the filter grating and the source is less than 500 mm.
- Embodiment 83 The system according to any of embodiments 61-80, wherein a distance between the filter grating and the source is less than 250 mm.
- Embodiment 84 The system according to any of embodiments 61-83, wherein the source is an X-ray tube.
- Embodiment 85 A method of performing X-ray CT imaging, the method comprising:
- Embodiment 86 The method according to embodiment 85, wherein the patient is a mammal.
- Embodiment 87 The method according to any of embodiments 85-86, wherein the patient is a human.
- Embodiment 88 The system according to any of embodiments 1-52 and 61-84, further comprising:
- a (non-transitory) machine-readable medium e.g., a computer-readable medium
- machine-executable e.g., computer-executable
- Embodiment 89 The system according to embodiment 88, wherein the image reconstruction is based on a non-linear X-ray data generation model.
- Embodiment 90 The system according to any of embodiments 88-89, wherein the image reconstruction comprises non-linear data modeling and compressed sensing.
- Embodiment 91 The method according to any of embodiments 53-60 and 85-87, wherein the system further comprises:
- a (non-transitory) machine-readable medium e.g., a computer-readable medium
- machine-executable e.g., computer-executable instructions
- the method further comprises performing the image reconstruction.
- Embodiment 92 The method according to embodiment 91, wherein the image reconstruction is based on a non-linear X-ray data generation model.
- Embodiment 93 The method according to any of embodiments 91-92, wherein the image reconstruction comprises non-linear data modeling and compressed sensing.
- Embodiment 94 The system according to any of embodiments 1-52, and 88-90, wherein the absorption grating is disposed between the filter grating and the source.
- Embodiment 95 The system according to any of embodiments 1-52, 61-84, and 88-90, wherein the filter grating is disposed between the absorption grating and the source.
- Embodiment 96 The system according to any of embodiments 1-52, 61-84, 88-90, 94, and 95, wherein the filter grating is positioned closer to the source than it is to the detector.
- a system for performing X-ray computed tomography (CT) imaging comprising: an X-ray source; a detector for detecting X-ray radiation from the source; a filter grating disposed between the source and the detector to modify an X-ray energy spectrum of the X-ray radiation into two or more spectra, the filter grating comprising a first curvature; and an absorption grating aligned with the filter grating to selectively block at least a portion of the X-ray radiation, the absorption grating having a second curvature that is concentric with the curvature of the filter grating in relation to the X-ray source; wherein at least one of the absorption grating and the filter grating is configured to move relative to the other during operation of the source.
- CT computed tomography
- the filter grating and the absorption grating each are substantially cylindrical in shape and are positioned such that the X-ray source lies approximately on the axis of each cylinder. In some embodiments, the system further comprises that the filter grating and the absorption grating each are substantially at least a portion of a sphere in shape and are positioned such that the X-ray source lies approximately at the center of each sphere. In some embodiments, the filter grating is at least a portion of a hemisphere.
- the system further comprises that the filter grating comprises: a set of first filter regions; a set of second filter regions; and a set of absorbing regions comprising an X-ray blocking material; wherein the first and second filter regions produce different X-ray spectra from the X-ray radiation; and wherein the first and second filter regions are positioned in an alternating fashion in the filter grating and the absorbing regions are positioned between each neighboring first and second filter regions.
- the movement of the at least one of the absorption grating and the filter grating is along a curved path that is parallel to the curvature of the absorption grating and the filter grating. In some embodiments, the movement of the at least one of the absorption grating and the filter grating is a rotation about an axis running substantially from the X-ray source to an approximate center of the absorption grating or the filter grating. In some embodiments, the X-ray source is pulsed.
- a system for performing X-ray computed tomography (CT) imaging comprising; an X-ray source; a detector for detecting X-ray radiation from the source; a filter grating, comprising; a set of first filter regions, the first filter regions adapted to produce a first X-ray spectrum from the X-ray radiation; a set of second filter regions, the second filter regions adapted to produce a second X-ray spectrum from the X-ray radiation, the second X-ray spectrum being different from the first X-ray spectrum; and a set of absorbing regions comprising an X-ray blocking material; and an absorption grating aligned with the filter grating to selectively block at least a portion of the X-ray radiation; wherein the first and second filter regions are positioned in an alternating fashion in the filter grating and the absorbing regions are positioned between each neighboring first and second filter regions; and wherein at least one of the absorption grating and the
- the filter grating and the absorption grating are substantially planar.
- the filter grating comprises a first curvature and the absorption grating comprises a second curvature that is concentric to the first curvature in relation to the X-ray source.
- the filter grating and the absorption grating are substantially at least a portion of a sphere.
- the filter grating is moved relative to the absorption grating in substantially only one direction during operation of the source.
- the filter grating is rotated about an axis running substantially from the X-ray source to an approximate center of the absorption grating or the filter grating.
- the filter grating is moved by at least one reel.
- a system for performing X-ray computed tomography (CT) imaging comprising: an X-ray source; a detector for detecting X-ray radiation from the source; a filter grating disposed between the source and the detector to modify an X-ray energy spectrum of the X-ray radiation into two or more spectra; and an absorption grating aligned with the filter grating to selectively block at least a portion of the X-ray radiation; wherein at least one of the absorption grating and the filter grating is configured to move in substantially only one direction relative to the other during operation of the source.
- CT computed tomography
- the filter grating is rotated relative to the absorption grating about an axis running substantially from the X-ray source to an approximate center of the absorption grating or the filter grating. In some embodiments, the filter grating is moved relative to the absorption grating by at least one reel. In some embodiments, the system further comprises that the filter grating and the absorption grating each are each substantially at least a portion of a sphere in shape and are positioned such that the X-ray source lies approximately at the center of each sphere; and wherein the axis of rotation of the filter grating runs substantially from the X-ray source to an approximate center of the filter grating.
- the system further comprises: a set of first filter regions; a set of second filter regions; and a set of absorbing regions comprising an X-ray blocking material; wherein the first and second filter regions produce different X-ray spectra from the X-ray radiation; and wherein the first and second filter regions are positioned in an alternating fashion in the filter grating and the absorbing regions are positioned between each neighboring first and second filter regions.
- the filter grating comprises a first curvature and the absorption grating comprises a second curvature that is concentric to the first curvature in relation to the X-ray source.
- Numerical simulations were carried out to evaluate GOLF systems and methods of embodiments of the subject invention, both for kVp-switching and non-kVp-switching dual-energy CT systems. Water and bone were selected as basis materials, and images were reconstructed via conventional filtered-back-projection without pre- and post-processing steps.
- a CT imaging simulation platform was implemented to evaluate the performance of the proposed filtration methods. In the simulation, 140 kVp was set for single-kVp (non-kVp-switching) dual-energy CT, and 80 kVp and 140 kVp X-rays were used for kVp-switching dual-energy CT scanning.
- the distance between the X-ray focal spot and the rotation center was set to 500 mm
- the distance between the X-ray focal spot and the flat-panel detector was set to 900 mm.
- the field-of view was set to 320 mm with 512 ⁇ 512 pixels and 0.625 mm pixel size.
- the chest phantom depicted in FIG. 8 was used, in which titanium-material rods were inserted, as indicated by the large (white) dots near the bottom middle of the phantom.
- SNR signal-to-noise ratio
- a GOLF k system/method was simulated for kVn-switching based dual-energy CT.
- 1,440 projections were collected where half of the data were at 80 kVp and the other half were at 140 kVp.
- the filter grating used 0.0 mm (air) and 1.0 mm thick tin with a duty cycle of 50%.
- the thickness of the X-ray absorption grating was 1 mm gold material allowing 99.995% absorption of X-rays at 100 keV.
- the duty cycle was changed from 10% to 100%, with a duty cycle of 100% being equivalent to conventional kVp-switching imaging.
- the monochromatic images were reconstructed according to Equation 14.
- FIG. 9 shows the reconstructed monochromatic images for this example.
- the first row presents images at 100 keV at different absorption grating duty cycles, as listed above each column.
- the first column is for a duty cycle of 100% (equivalent to conventional kVp-switching imaging).
- the second row shows results at 120 keV at different absorption grating duty cycles.
- FIG. 10 shows the local metal areas (the areas around the rods represented by the dots near the lower-middle section of the phantom) of the images from FIG. 9 .
- the rows and columns in FIG. 10 are for the same energy/duty cycle combinations as in FIG. 9 .
- FIG. 13A shows the SNR values for the images of FIG. 9 .
- the cross data points are for an energy of 100 keV
- the circle data points are for an energy of 120 keV
- the y-axis shows the SNR
- the x-axis shows the different duty cycles investigated.
- the first column for each shows the performance that is equivalent to conventional kVp-switching dual-energy CT.
- FIG. 13A with a smaller absorption grating opening, the low- and high-energy X-ray spectra have better separation, leading to better image quality, in particular in terms of beam-hardening reduction.
- a GOLF c system/method was simulated for single-kVp-based (non-kVp-switching) dual-energy CT.
- 1,440 projections were collected at 140 kVp.
- the filter grating used 0.1-mm tin and 1.0-mm tin in the two strip tiller, and 0.0-mm tin (air) and 1.0-mm tin with 50% duty cycle in the multi-strip grating.
- the monochromatic images were reconstructed according to Equation 14.
- FIG. 11 shows the reconstructed monochromatic images for this example.
- the first row presents images at 100 keV at different absorption grating duty cycles for multi-strip gratings (in the first three columns) and for a two-strip grating (in the fourth column), as listed above each column.
- the second row shows results at 120 keV.
- FIG. 12 shows the local metal areas (the areas around the rods represented by the dots near the lower-middle section of the phantom) of the images from FIG. 11 .
- the rows and columns in FIG. 12 are for the same energy/duty cycle combinations as in FIG. 11 .
- FIG. 13B shows the SNR values for the images of FIG. 11 .
- FIG. 13B shows the SNR values for the images of FIG. 11 .
- the cross data points are for an energy of 100 keV
- the circle data points are for an energy of 120 keV
- the y-axis shows the SNR
- the x-axis shows the different duty cycles investigated for the multi-strip gratings (first three marks on x-axis) and the two-strip grating (right-most mark on x-axis).
- FIGS. 11 and 12 there are some artifacts in the central area of the images with the two-strip grating method (far right column in each of FIGS. 11 and 12 ). They were caused by the data interpolation in the sinogram, which can be avoided by advanced algorithms, such as iterative reconstruction schemes (see also reference [24] in the References section, which is hereby incorporated herein by reference in its entirety). Overall, the two-strip grating approach has a similar performance to that of the 50% duty cycle multi-strip grating approach.
- the kVp-switching method results in better performance across the board in terms of beam-hardening reduction and SNR, which is consistent with its improved spectrum separation demonstrated by comparing FIGS. 5A-5C with FIGS. 7A-7B . Also, with the GOLF k system/method, a smaller absorption grating opening (smaller duty cycle) leads to SNR performance for a given radiation dose to the patient, but at the same time reduces the X-ray source efficacy.
- a GOLF k system/method was simulated for kVp-switching based dual-energy CT, including collecting 360, 720, 1080 projections of each energy X-rays in turn.
- the thickness of the X-ray absorption grating was 1 mm gold materials having 99.995% absorption of X-rays at 100 keV.
- the two filtration materials for 80 kVp and 140 kVp X-rays were air and tin, respectively.
- the thickness of tin material was set to 0 mm, 0.25 mm, and 0.5 mm in different experiments.
- the vibration frequency of the filter grating was set to match the switching frequency of X-ray energies in the X-ray source.
- FIG. 14 shows the reconstructed monochromatic images.
- the first column presents images at energies of 60 keV, 80 keV and 100 keV (in the first, second, and third rows, respectively) with 0.5 mm tin and 0.5 mm tin (i.e., a conventional kVp-switching method).
- the right-most columns show the results for air and 0.5 mm tin (middle column) and air and 1 mm fin (right-most column).
- FIG. 15 shows a plot of SNR for these images.
- the cross data points are for the conventional kVp-switching method
- the circle data points are for the air/1 mm tin GOLF k system/method
- the star data points are for the air/0.5 mm tin GOLF k system/method.
- the upper-most (green) line shows connects the star data points
- the middle-most (red) line connects the circle data points
- the lower-most (blue) line connects the cross data points.
- a GOLF k system/method was simulated for kVp-switching based dual-energy CT, including collecting 360, 720, 1080 projections of each energy X-rays in turn.
- the fixed filtration materials were air for 80 kVp X-rays and 0.5 mm tin for 140 kVp X-rays.
- the distance between focal spots was determined by the geometry of the CT scanner and the angular difference between neighboring projections. In the 360 projection setting, a uniform angular sampling around the circular trajectory was assumed, and the distance between neighboring 80 kVp and 140 kVp X-rays was 4.36 mm.
- the X-ray focal spots and corresponding filters were set to a distance of 4.36 mm accordingly to have the collected neighboring 80 kVp and 140 kVp projection pairs with the same projection angles. Results were obtained using the X-flying focal spot method.
- FIG. 16 shows a comparison of the 100 keV, 720-projection 0/0.5 mm Sn image from FIG. 14 for Example 3 (the bottom-middle image in FIG. 14 ) with the image obtained in this example at 100 keV, 720-projection.
- the first row shows the images
- the second row shows the error map: the first column is the image from Example 3, and the second column is the image from this example.
- FIG. 17 shows the images from this example across the top; images left to right are for 360, 720, and 1080 projections (100 keV, 0/0.5 mm Sn), respectively, and the plot at the lower portion of FIG. 17 shows a plot of the SNR vs. projection number.
- the circle data points are for this example (the three images at the top portion of FIG. 17 ) and are connected by the upper (red) line, and the cross data points are for Example 3 and are connected by the lower (blue) line.
- the cross data points are for 100 keV, 0/0.5 Sn at the three different numbers of projections. Referring to FIGS. 16 and 17 , it can be seen that a higher number of projections gives a better monochromatic image, and the X-flying focal spot method improves the results slightly.
- FIG. 18 shows plots of normalized spectra versus X-ray energy for tin and gold (top left, with the (blue) line that is higher at the left of the plot being for tin and the (red) line that is higher at the right of the plot being for gold) and for tin and gadolinium (top right, with the (blue) line that is higher at the left of the plot being for tin and the (red) line that is higher at the right of the plot being for gadolinium).
- a simulation experiment was performed to verify no increment in the apparent spot size or loss of the image resolution.
- the simulation setup is the same as shown in FIG. 20 .
- the focal spot size was set to 1 mm, and SGD and SDD were set to 100 mm and 1000 mm respectively.
- an absorption grating period of 0.225 mm will give a uniform illumination on the detector array (after normalization for intensity fall-off due to source-to-pixel distance).
- An ideal zero-thickness absorption grating with a period of 0.225 mm and 50% duty cycle was used.
- X-rays were collected using an ideal 888-pixel detector array of 1 mm pixels.
- the 28A shows the detected (distance normalized) x-ray intensity profile across the detector array with and without the absorption grating.
- the intensity profiles are uniform in both the cases, except that the profile with the grating is just half of that without the grating. That is, the x-ray intensity with grating is 0.5 compared to the intensity without grating of 1.
- the system point spread function was measured by placing an ideal high-absorption 0.5 mm rod at the center of the imaging field of view.
- FIG. 28B shows the projection seen at the detector with and without the absorption grating.
- the PSF convolved profiles account for the focal spot distribution, the absorption grating, and the 0.5 mm-diameter rod.
- the PSF with the grating is virtually identical to the PSF without the grating, without any observable effect of the GOLF gratings on the image resolution.
- FIG. 30A shows the filter thicknesses and system type for each simulation.
- FIG. 30B shows the resulting CNR values.
- GOLF2 used Air as the low-pass filter for the 80 kVp views, and 0.7 mm Tin as the high-pass filter for the 140 kVp views.
- the resulting water-blood CNR was 2.8, the best of the simulation results.
- GOLF2 has produced significantly higher CNR than either kVp1 or kVp2, and kVp2 had a dramatic low-kVp flux inefficiency due to attenuation by the 0.5 mm Tin filter.
- FIG. 31 shows 100 keV monochromatic reconstructions for the kVp1, GOLF1 and Dual1 simulations in FIG. 30 .
- the reconstruction images for the other 3 simulations look very similar except for residual beam hardening near the metal rods.
Landscapes
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Medical Informatics (AREA)
- Radiology & Medical Imaging (AREA)
- Molecular Biology (AREA)
- Biophysics (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Optics & Photonics (AREA)
- Pathology (AREA)
- Physics & Mathematics (AREA)
- Biomedical Technology (AREA)
- Heart & Thoracic Surgery (AREA)
- High Energy & Nuclear Physics (AREA)
- Surgery (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Pulmonology (AREA)
- Theoretical Computer Science (AREA)
- Computer Vision & Pattern Recognition (AREA)
- Apparatus For Radiation Diagnosis (AREA)
Abstract
Description
S a(E)=S T(E)[F c(E)A eff +F w(E)(1−A eff)], (1)
where n is a positive integer. With planar gratings and a planar detector array, every detector pixel has the same ratio SGD/SDD. When Eq. (3) is satisfied, every detector pixel gets the same percentage of flux blocked by the grating. That is, if Eq. (3) is satisfied and the grating duty cycle of 50% is used, then exactly ½ of the focal spot is blocked by the absorption grating for every point on the detector. When Eq. (3) is not satisfied, there is grating-induced flux variation across the detector array. As the integer n grows larger, the grating-induced variations diminish even when Eq. (3) is net satisfied. If necessary, this variation could be allowed to remain and be accounted in the common CT air and spectral calibrations.
For 30 keV x-rays, λ=4.13E−10. With an open slit width of 50 um, Eq. (4) gives the diffraction as bounded between +/−8.26E−6 radians. Thus, all x-ray energies above 30 keV stays within +/−8.26E−6 radians on leaving any slit larger than 50 um. Therefore, x-rays continue straight through the slit and, with an SDD of only ˜1 meter, there is little interaction with radiation from other slits.
d(t)=D peak sin(2πft) (5)
v(t)=2πfD peak cos(2πft) (6)
a(t)=−(2πf)2 D peak
W m=abs(T f tan θ). (10)
where “L” and “H” indicate low- and high-energy, respectively, and “1” and “2” indicate the two basis materials, respectively. Mass densities (p1, p2) of the two basis materials are used to characterize any material. In the projection domain (p) and image domain (μ), there are low- and high-energy datasets and images (pL, pH and μL, μH). The monochromatic image CT(E) at any x-ray energy E can be reconstructed from projections.
(2) P(E)=w(E)·P L+(1−w(E))·P H. (12)
Specifically,
(3) CT(E)=recon(P(E)) (13)
and
(4) CT(E)=w(E)·CT L+(1−w(E))·CT H, (14)
where the weighting factor is
where Ā is the average over a region of interest (ROI), and σ is the standard variation in the ROI, to quantify a monochromatic image. In
where Ā is the average over a region of interest (ROI), and σ is the standard deviation within the ROI.
- [1] W. A. Kalender, “X-ray computed tomography,” Physics in medicine and biology, vol. 51, p. R29, 2006.
- [2] G. Wang, H. Yu, and B. De Man, “An outlook on x-ray CT research and development.” Medical physics, vol. 35, pp. 1051-1064, 2008.
- [3] G. Wang, T.-H. Lin, P.-c. Cheng, and D. M. Shinozaki, “A general cone-beam reconstruction algorithm,” Medical Imaging, IEEE Transactions on, vol. 12, pp. 486-496, 1993.
- [4] K. Taguchi and H. Aradate, “Algorithm for image reconstruction in multi-slice helical CT,” Medical Physics, vol. 25, pp. 550-561, 1998.
- [5] O. Wang, C. R. Crawford, and W. A. Kalender, “Guest editorial-Multirow detector and cone-beam spiral/helical CT,” Medical Imaging, IEEE Transactions on. vol. 19, pp. 817-821, 2000.
- [6] T. R. Johnson, B. Krauss, M. Sedlmair, M. Grasruck, H. Bruder, D. Morhard, et al., “Material differentiation by dual energy CT: initial experience.” European radiology, vol. 17, pp. 1510-1517, 2007.
- [7] A. Chaser, T. R. Johnson, H. Chandarana, and M. Macari, “Dual energy CT: preliminary observations and potential clinical applications in the abdomen,” European radiology, vol. 19, pp. 13-23, 2009.
- [8] L. Yu, S. Leng, and C. H. Mccollough, “Dual-energy CT-based monochromatic imaging,” Air American Journal of Roentgenology, vol. 199, pp. S9-S15, 2012.
- [9] M. Karcaaltincaba and A. Aktas, “Dual-energy CT revisited with multidetector CT: review of principles and clinical applications,” Diagnostic & Interventional Radiology, vol. 17, pp. 181-94, 2010.
- [10] J. Schlomka, E. Roessl, R. Dorscheid, S. Dill, G. Martens, T. Istel, et al., “Experimental feasibility of multi-energy photon-counting K-edge imaging in pre-clinical computed tomography,” Physics in medicine and biology, vol. 53, p. 4031, 2008.
- [11] W. C. Barber, E. Nygard. J. S. Iwanczyk, M. Zhang, E. C. Frey, B. M. Tsui, et al., “Characterization of a novel photon counting detector for clinical CT: count rate, energy resolution, and noise performance,” in SPIE Medical Imaging, 2009, pp. 725824-725824-9.
- [12] H. Gao, H. Yu, S. Osher, and G. Wang, “Multi-energy CT based on a prior rank, intensity and sparsity model (PRISM),” Inverse problems, vol. 27, p. 115012, 2011.
- [13] J. Fomaro, S. Leschka, D. Hibbeln, A. Butler, N. Anderson, G. Pache, et al., “Dual- and multienergy CT: approach to functional imaging,” Insights Into Imaging, vol. 2, pp. 149-159, 2011.
- [14] B. Li, G. Yadava, and J. Hsieh. “Quantification of head and body CTDIVOL of dual-energy x-ray CT with fast-kVp switching,” Medical Physics, vol. 38, pp. 2595-601, 2011.
- [15] R. Carmi, G. Naveh, and A. Altman, “Material separation with dual-layer CT,” IEEE Nuclear Science Symposium Conference Record Nuclear Science Symposium, vol. 4, 2005.
- [16] T. G. Flohr, C. H. Mccollough, H. Bruder, M. Petersilka, K. Gruber, C. Suβ, et al., “et al. First performance evaluation of a dualsource CT (DSCT) system,” European Radiology, vol. 16, pp. 256-68, 2006.
- [17] M. Petersilka, H. Bruder, B. Krauss, K. Stierstorfer, and T. G. Flohr, “Technical principles of dual source CT,” European Journal of Radiology, vol. 68, pp. 362-368, 2008.
- [18] M. Grasruck, S. Kappler, M. Reinwand, and K. Stierstorfer, “Dual energy with dual source CT and kVp switching with single source CT: A comparison of dual energy performance,” Proceedings of SPIE—The International Society for Optical Engineering, vol. 7258, 2009.
- [19] T. G. Flohr, K. Stierstorfer, S. Ulzheimer, H. Bruder, A, N. Primak, and C. H. Mccollough, “Image reconstruction and image quality evaluation for a 64-slice CT scanner with z-flying local spot,” Medical Physics, vol. 32, pp. 2536-47, 2005.
- [20] G. Wang, “X-ray micro-CT with a displaced detector array,” Medical Physics, vol. 29, pp. 1634-6, 2002.
- [21] V. Liu, N. R. Lariviere, and G. Wang, “X-ray micro-CT with a displaced detector array: application to helical cone-beam reconstruction,” Medical Physics, vol. 30, pp. 2758-61, 2003.
- [22] Q. Yang, W. Cong, Y. Xi, and G. Wang, “Spectral X-ray CT Reconstruction with Combination of Energy-integrating and Photon-counting Modules,” Plos ONE, 2016.
- [23] L. Yu, J. A. Christner, S. Leng, J. Wang, J. G. Fletcher, and C. H. Mccollough. “Virtual monochromatic imaging in dual-source dual-energy CT: Radiation dose and image quality,” Medical Physics, vol. 38, pp. 6371-9, 2011.
- [24] M. Beister, D. Kolditz, and W. A. Kalender. “Iterative reconstruction methods in X-ray CT,” Physica Medica, vol. 28, pp. 94-108, 2012.
- [25] M. J. Kang, C. M. Park, C. H. Lee, J. M. Goo, and H. J. Lee, “Dual-energy CT: clinical applications in various pulmonary diseases,” Radiographics, vol. 30, pp. 685-98, 2010.
- [26] Wang et al., International Patent Application Publication No. WO2016/106348.
- [27] Wang et al., U.S. Patent Application Publication No. 2015/0157286.
- [28] Wang et al., U.S. Patent Application Publication No. 2015/0170361.
- [29] Wang et al., U.S. Patent Application Publication No. 2015/0193927.
- [30] Wang et al., International Patent Application Publication No. WO2015/164405.
- [31] Wang et al., U.S. Patent Application Publication No. 2016/0113602.
- [32] Wang et al., U.S. Patent Application Publication No. 2016/0135769.
- [33] Wang et al., U.S. Patent Application Publication No. 2016/0166852.
- [34] Wang et al., International Patent Application Publication No. WO2016/106348.
- [35] Wang et al., International Patent Application Publication No. WO2016/118960.
- [36] Wang et al., International Patent Application Publication No. WO2016/154136.
- [37] Wang et al., International Patent Application Publication No. WO2016/197127.
- [38] Wang et al., International Patent Application Publication No. WO2017/015381.
- [39] Wang et al., International Patent Application Publication No. WO2017/019782.
- [40] Wang et al., International Patent Application No. PCT/US2016/051755.
- [41] Wang et al., International Patent Application No. PCT/US2016/061890.
- [42] Wang et al., International Patent Application No. PCT/US2017/018456.
Claims (19)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US16/294,438 US11051772B2 (en) | 2016-04-08 | 2019-03-06 | Filtration methods for dual-energy X-ray CT |
US17/354,286 US11701073B2 (en) | 2016-04-08 | 2021-06-22 | Filtration methods for dual-energy X-RAY CT |
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201662319881P | 2016-04-08 | 2016-04-08 | |
US201662333882P | 2016-05-10 | 2016-05-10 | |
PCT/US2017/026322 WO2017176976A1 (en) | 2016-04-08 | 2017-04-06 | Rapid filtration methods for dual-energy x-ray ct |
US201862638984P | 2018-03-06 | 2018-03-06 | |
US16/294,438 US11051772B2 (en) | 2016-04-08 | 2019-03-06 | Filtration methods for dual-energy X-ray CT |
Related Parent Applications (3)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US16/092,393 Continuation US11337663B2 (en) | 2016-04-08 | 2017-04-06 | Rapid filtration methods for dual-energy X-ray CT |
PCT/US2017/026322 Continuation WO2017176976A1 (en) | 2016-04-08 | 2017-04-06 | Rapid filtration methods for dual-energy x-ray ct |
US201816092393A Continuation | 2016-04-08 | 2018-10-09 |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US17/354,286 Continuation US11701073B2 (en) | 2016-04-08 | 2021-06-22 | Filtration methods for dual-energy X-RAY CT |
Publications (2)
Publication Number | Publication Date |
---|---|
US20190269375A1 US20190269375A1 (en) | 2019-09-05 |
US11051772B2 true US11051772B2 (en) | 2021-07-06 |
Family
ID=67768925
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US16/294,438 Active 2037-11-23 US11051772B2 (en) | 2016-04-08 | 2019-03-06 | Filtration methods for dual-energy X-ray CT |
US17/354,286 Active 2037-05-29 US11701073B2 (en) | 2016-04-08 | 2021-06-22 | Filtration methods for dual-energy X-RAY CT |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US17/354,286 Active 2037-05-29 US11701073B2 (en) | 2016-04-08 | 2021-06-22 | Filtration methods for dual-energy X-RAY CT |
Country Status (1)
Country | Link |
---|---|
US (2) | US11051772B2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20210321961A1 (en) * | 2016-04-08 | 2021-10-21 | Rensselaer Polytechnic Institute | Filtration methods for dual-energy x-ray ct |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP7044764B6 (en) * | 2016-09-08 | 2022-05-31 | コーニンクレッカ フィリップス エヌ ヴェ | Source grid for X-ray imaging |
CN111839562B (en) * | 2020-06-19 | 2023-04-11 | 东软医疗系统股份有限公司 | Ray data processing method and device, storage medium and electronic equipment |
Citations (22)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5838758A (en) | 1990-08-10 | 1998-11-17 | Vivid Technologies | Device and method for inspection of baggage and other objects |
US6108403A (en) | 1998-04-21 | 2000-08-22 | Picker International, Inc. | X-ray equalization filter |
US6633627B2 (en) * | 2000-09-28 | 2003-10-14 | Ge Medical Systems Global Technology Company, Llc | X-ray CT system, gantry apparatus, console terminal, method of controlling them, and storage medium |
US6993117B2 (en) | 2002-04-22 | 2006-01-31 | General Electric Company | Method and apparatus of modulating the filtering of radiation during radiographic imaging |
US7082189B2 (en) * | 2003-07-15 | 2006-07-25 | Ge Medical Systems Global Technology Company, Llc | X-ray distribution adjusting filter apparatus and X-ray CT apparatus using the same |
US7539284B2 (en) | 2005-02-11 | 2009-05-26 | Besson Guy M | Method and system for dynamic low dose X-ray imaging |
US8287187B2 (en) | 2010-06-21 | 2012-10-16 | Miller Zachary A | Adjustable dynamic X-ray filter |
US20130251100A1 (en) * | 2012-03-23 | 2013-09-26 | Rigaku Corporation | X-ray composite apparatus |
US20130272504A1 (en) | 2012-04-16 | 2013-10-17 | Meir Deutsch | X-Ray Dose Reduction by Controlled Shutter Speed |
US8679102B2 (en) | 2011-02-03 | 2014-03-25 | Tria Beauty, Inc. | Devices and methods for radiation-based dermatological treatments |
US20140112441A1 (en) * | 2012-10-18 | 2014-04-24 | Klinikum Der Universitate Munchen | Selection of a radiation shaping filter |
US20140185746A1 (en) * | 2012-12-28 | 2014-07-03 | Pavlo Baturin | Spectral grating-based differential phase contrast system for medical radiographic imaging |
US8917815B2 (en) | 2010-06-21 | 2014-12-23 | Zachary A. Miller | Adjustable dynamic filter |
US8995615B2 (en) | 2012-08-02 | 2015-03-31 | Canon Kabushiki Kaisha | Specimen information acquisition system |
US9125572B2 (en) | 2012-06-22 | 2015-09-08 | University Of Utah Research Foundation | Grated collimation system for computed tomography |
US9204852B2 (en) | 2013-12-31 | 2015-12-08 | General Electric Company | Systems and methods for increased energy separation in multi-energy X-ray imaging |
US9312040B2 (en) | 2012-05-31 | 2016-04-12 | Siemens Aktiengesellschaft | Adaptive x-ray filter for changing the local intensity of x-rays |
US9320481B2 (en) | 2014-03-31 | 2016-04-26 | General Electric Company | Systems and methods for X-ray imaging |
US9439612B2 (en) | 2013-04-02 | 2016-09-13 | Triple Ring Technologies, Inc. | Method and apparatus for variable X-ray filtration |
US9504439B2 (en) | 2013-10-07 | 2016-11-29 | Samsung Electronics Co., Ltd. | X-ray imaging apparatus and control method for the same |
US20170273642A1 (en) * | 2014-09-08 | 2017-09-28 | Koninklijke Philips N.V. | Systems and methods for grating modulation of a spectra and intensity in computed tomography |
US9991014B1 (en) | 2014-09-23 | 2018-06-05 | Daniel Gelbart | Fast positionable X-ray filter |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9101272B2 (en) * | 2011-03-24 | 2015-08-11 | Jefferson Radiology, P.C. | Fixed anterior gantry CT shielding |
US11051772B2 (en) * | 2016-04-08 | 2021-07-06 | Rensselaer Polytechnic Institute | Filtration methods for dual-energy X-ray CT |
-
2019
- 2019-03-06 US US16/294,438 patent/US11051772B2/en active Active
-
2021
- 2021-06-22 US US17/354,286 patent/US11701073B2/en active Active
Patent Citations (22)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5838758A (en) | 1990-08-10 | 1998-11-17 | Vivid Technologies | Device and method for inspection of baggage and other objects |
US6108403A (en) | 1998-04-21 | 2000-08-22 | Picker International, Inc. | X-ray equalization filter |
US6633627B2 (en) * | 2000-09-28 | 2003-10-14 | Ge Medical Systems Global Technology Company, Llc | X-ray CT system, gantry apparatus, console terminal, method of controlling them, and storage medium |
US6993117B2 (en) | 2002-04-22 | 2006-01-31 | General Electric Company | Method and apparatus of modulating the filtering of radiation during radiographic imaging |
US7082189B2 (en) * | 2003-07-15 | 2006-07-25 | Ge Medical Systems Global Technology Company, Llc | X-ray distribution adjusting filter apparatus and X-ray CT apparatus using the same |
US7539284B2 (en) | 2005-02-11 | 2009-05-26 | Besson Guy M | Method and system for dynamic low dose X-ray imaging |
US8287187B2 (en) | 2010-06-21 | 2012-10-16 | Miller Zachary A | Adjustable dynamic X-ray filter |
US8917815B2 (en) | 2010-06-21 | 2014-12-23 | Zachary A. Miller | Adjustable dynamic filter |
US8679102B2 (en) | 2011-02-03 | 2014-03-25 | Tria Beauty, Inc. | Devices and methods for radiation-based dermatological treatments |
US20130251100A1 (en) * | 2012-03-23 | 2013-09-26 | Rigaku Corporation | X-ray composite apparatus |
US20130272504A1 (en) | 2012-04-16 | 2013-10-17 | Meir Deutsch | X-Ray Dose Reduction by Controlled Shutter Speed |
US9312040B2 (en) | 2012-05-31 | 2016-04-12 | Siemens Aktiengesellschaft | Adaptive x-ray filter for changing the local intensity of x-rays |
US9125572B2 (en) | 2012-06-22 | 2015-09-08 | University Of Utah Research Foundation | Grated collimation system for computed tomography |
US8995615B2 (en) | 2012-08-02 | 2015-03-31 | Canon Kabushiki Kaisha | Specimen information acquisition system |
US20140112441A1 (en) * | 2012-10-18 | 2014-04-24 | Klinikum Der Universitate Munchen | Selection of a radiation shaping filter |
US20140185746A1 (en) * | 2012-12-28 | 2014-07-03 | Pavlo Baturin | Spectral grating-based differential phase contrast system for medical radiographic imaging |
US9439612B2 (en) | 2013-04-02 | 2016-09-13 | Triple Ring Technologies, Inc. | Method and apparatus for variable X-ray filtration |
US9504439B2 (en) | 2013-10-07 | 2016-11-29 | Samsung Electronics Co., Ltd. | X-ray imaging apparatus and control method for the same |
US9204852B2 (en) | 2013-12-31 | 2015-12-08 | General Electric Company | Systems and methods for increased energy separation in multi-energy X-ray imaging |
US9320481B2 (en) | 2014-03-31 | 2016-04-26 | General Electric Company | Systems and methods for X-ray imaging |
US20170273642A1 (en) * | 2014-09-08 | 2017-09-28 | Koninklijke Philips N.V. | Systems and methods for grating modulation of a spectra and intensity in computed tomography |
US9991014B1 (en) | 2014-09-23 | 2018-06-05 | Daniel Gelbart | Fast positionable X-ray filter |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20210321961A1 (en) * | 2016-04-08 | 2021-10-21 | Rensselaer Polytechnic Institute | Filtration methods for dual-energy x-ray ct |
US11701073B2 (en) * | 2016-04-08 | 2023-07-18 | Rensselaer Polytechnic Institute | Filtration methods for dual-energy X-RAY CT |
Also Published As
Publication number | Publication date |
---|---|
US20190269375A1 (en) | 2019-09-05 |
US20210321961A1 (en) | 2021-10-21 |
US11701073B2 (en) | 2023-07-18 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US11701073B2 (en) | Filtration methods for dual-energy X-RAY CT | |
US12036055B2 (en) | Rapid filtration methods for dual-energy X-ray CT | |
US7324623B2 (en) | Computed tomography scanner with large gantry bore | |
Kalender | Computed tomography: fundamentals, system technology, image quality, applications | |
Mahesh | MDCT physics: the basics: technology, image quality and radiation dose | |
JP3782833B2 (en) | Computerized tomographic imaging device | |
JP4740516B2 (en) | Cone and inclined parallel sampling and reconstruction method and apparatus | |
CN107106108B (en) | X-ray CT apparatus, projection data up-sampling method, and image reconstruction method | |
JPH07204195A (en) | Ct scanner device, its application method and ct scan method | |
US6426989B2 (en) | Computed tomography method | |
CN105960204A (en) | Mammography imaging arrangement for tomosynthesis | |
JP2013052232A (en) | Method of dose reduction for computed tomography (ct) imaging and apparatus for implementing the same | |
JP2009082250A (en) | X-ray ct apparatus | |
US7778387B2 (en) | Reconstruction method for helical cone-beam CT | |
US20100202583A1 (en) | Systems and Methods for Exact or Approximate Cardiac Computed Tomography | |
EP1478273B1 (en) | Sequential computed tomography method | |
JP4701038B2 (en) | X-ray CT system | |
EP0849711B1 (en) | Method and apparatus for cone beam imaging | |
JP4172201B2 (en) | Radiation imaging apparatus and radiation image forming apparatus | |
JP2006263225A (en) | X-ray tomography equipment | |
Xi et al. | Grating oriented line-wise filtration (GOLF) for dual-energy x-ray CT | |
JP4732592B2 (en) | Optimized CT protocol | |
US9757088B2 (en) | Detector apparatus for cone beam computed tomography | |
JPH119582A (en) | X-ray computerized tomograph | |
JPH0471540A (en) | X-ray ct device |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
FEPP | Fee payment procedure |
Free format text: ENTITY STATUS SET TO UNDISCOUNTED (ORIGINAL EVENT CODE: BIG.); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY |
|
FEPP | Fee payment procedure |
Free format text: ENTITY STATUS SET TO SMALL (ORIGINAL EVENT CODE: SMAL); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NON FINAL ACTION MAILED |
|
AS | Assignment |
Owner name: RENSSELAER POLYTECHNIC INSTITUTE, NEW YORK Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HARRISON, DANIEL DAVID;WANG, GE;REEL/FRAME:055392/0229 Effective date: 20210224 |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NOTICE OF ALLOWANCE MAILED -- APPLICATION RECEIVED IN OFFICE OF PUBLICATIONS |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: PUBLICATIONS -- ISSUE FEE PAYMENT RECEIVED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: PUBLICATIONS -- ISSUE FEE PAYMENT VERIFIED |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |